Biorheology - Volume 43, issue 5

Authors: Suzuki, Toru | Toyoda, Takashi | Suzuki, Hiroshi | Hisamori, Noriyuki | Matsumoto, Hideo | Toyama, Yoshiaki

Article Type: Research Article

Abstract: There have been few reports describing the effects of mechanical loading on the metabolism of meniscal cells. The aim of this study was to investigate the effects of hydrostatic pressure on meniscal cell metabolism. Human meniscal cells were cultured in alginate beads for 3 days. They were then subjected to 4 MPa hydrostatic pressure for 4 hours in either a static or cyclic (1 Hz) mode using a specially designed and constructed system. Immediately after the pressure application, the messenger RNA levels for aggrecan, type I collagen, matrix metalloproteinases (MMP) -1, -3, -9, -13 and tissue inhibitors of metalloproteinases (TIMP) …-1 and -2 were measured. It was found that the application of static hydrostatic pressure caused a significant decrease in mRNA expression for MMP-1 and -13 (p<0.05). In contrast, the application of cyclic hydrostatic pressure was associated with a significant increase in type I collagen (p<0.01), TIMP-1 and -2 mRNA expression (p<0.01). These results would suggest that hydrostatic pressure in isolation can modulate mRNA expressions for matrix proteins in meniscal cells. Show more

Keywords: Meniscal cells, hydrostatic pressure, mRNA expression, mechanical stress, extracellular matrix

Citation: Biorheology, vol. 43, no. 5, pp. 611-622, 2006

Authors: Hrapko, M. | van Dommelen, J.A.W. | Peters, G.W.M. | Wismans, J.S.H.M.

Article Type: Research Article

Abstract: The non-linear mechanical behaviour of porcine brain tissue in large shear deformations is determined. An improved method for rotational shear experiments is used, producing an approximately homogeneous strain field and leading to an enhanced accuracy. Results from oscillatory shear experiments with a strain amplitude of 0.01 and frequencies ranging from 0.04 to 16 Hz are given. The immediate loss of structural integrity, due to large deformations, influencing the mechanical behaviour of brain tissue, at the time scale of loading, is investigated. No significant immediate mechanical damage is observed for these shear deformations up to strains of 0.45. Moreover, the material …behaviour during complex loading histories (loading–unloading) is investigated. Stress relaxation experiments for strains up to 0.2 and constant strain rate experiments for shear rates from 0.01 to 1 s−1 and strains up to 0.15 are presented. A new differential viscoelastic model is used to describe the mechanical response of brain tissue. The model is formulated in terms of a large strain viscoelastic framework and considers non-linear viscous deformations in combination with non-linear elastic behaviour. This constitutive model is readily applicable in three-dimensional head models in order to predict the mechanical response of the intra-cranial contents due to an impact. Show more

Keywords: Brain tissue, large strain, constitutive model, viscoelasticity

Citation: Biorheology, vol. 43, no. 5, pp. 623-636, 2006

Authors: Fang, Jiannong | Owens, Robert G.

Article Type: Research Article

Abstract: In the present paper we use a new constitutive equation for whole human blood [R.G. Owens, A new microstructure-based constitutive model for human blood, J. Non-Newtonian Fluid Mech. (2006), to appear] to investigate the steady, oscillatory and pulsatile flow of blood in a straight, rigid walled tube at modest Womersley numbers. Comparisons are made with the experimental results of Thurston [Elastic effects in pulsatile blood flow, Microvasc. Res. 9 (1975), 145–157] for the pressure drop per unit length against volume flow rate and oscillatory flow rate amplitude. Agreement in all cases is very good. In the presentation of the numerical …and experimental results we discuss the microstructural changes in the blood that account for its rheological behaviour in this simple class of flows. In this context, the concept of an apparent complex viscosity proves to be useful. Show more

Keywords: Aggregation, viscoelastic, thixotropic, pulsatile flow, Womersley, complex viscosity

Citation: Biorheology, vol. 43, no. 5, pp. 637-660, 2006

Authors: Khanafer, Khalil M. | Gadhoke, Prateek | Berguer, Ramon | Bull, Joseph L.

Article Type: Research Article

Abstract: Pulsatile flow in an axisymmetric rigid-walled model of an abdominal aorta aneurysm was analyzed numerically for various aneurysm dilations using physiologically realistic resting waveform at time-averaged Reynolds number of 300 and peak Reynolds number of 1607. Discretization of the governing equations was achieved using a finite element scheme based on the Galerkin method of weighted residuals. Comparisons with previously published work on the basis of special cases were performed and found to be in excellent agreement. Our findings indicate that the velocity fields are significantly affected by non-Newtonian properties in pathologically altered configurations. Non-Newtonian fluid shear stress is found to …be greater than Newtonian fluid shear stress during peak systole. Further, the maximum shear stress is found to occur near the distal end of AAA during peak systole. The impact of non-Newtonian blood flow characteristics on pressure compared to Newtonian model is found insignificant under resting conditions. Viscous and inertial forces associated with blood flow are responsible for the changes in the wall that result in thrombus deposition and dilation while rupture of AAA is more likely determined by much larger mechanical stresses imposed by pulsatile pressure on the wall of AAA. Show more

Keywords: Aneurysm, non-Newtonian, pulsatile, shear stress

Citation: Biorheology, vol. 43, no. 5, pp. 661-679, 2006

Authors: Kumar, R. Anand | Moake, Joel L. | Nolasco, Leticia | Bergeron, Angela L. | Sun, Carol | Dong, Jing-fei | McIntire, Larry V.

Article Type: Research Article

Abstract: Endothelial cells synthesize and secrete von Willebrand factor (VWF) multimers, including unusually large forms (ULVWF), which are usually cleaved into smaller multimers found in normal plasma (P-VWF). Thrombotic thrombocytopenic purpura (TTP) is a microangiopathic disorder characterized by systemic attachment of platelets to inadequately cleaved ULVWF multimers. We have compared ULVWF and P-VWF in their capacity to become immobilized onto surfaces in vitro and their ability to mediate platelet adhesion. We have also used functional assays to directly compare ULVWF forms with purified P-VWF in mediating platelet aggregation in solution. At comparable concentrations, ULVWF is more effectively adsorbed onto glass surfaces …than P-VWF and supports increased platelet adhesion. ULVWF is also significantly more potent than P-VWF in mediating both shear-induced platelet aggregation and ristocetin-mediated platelet agglutination. Show more

Keywords: TTP, ULVWF, platelet adhesion, aggregation

Citation: Biorheology, vol. 43, no. 5, pp. 681-691, 2006

Authors: Akers, W.J. | Cupps, J.M. | Haidekker, M.A.

Article Type: Correction

Citation: Biorheology, vol. 43, no. 5, pp. 693-693, 2006